Pellet cleaning for rotary air preheater



Nov. 6, 1962 G. D. BRADDON 3,062,508

PELLET CLEANING FOR ROTARY AIR PREHEATER Filed Jan. 9, 1961 INVENTOR. Gearge 5 550 0 0/7 BY United States Patent corporation of Delaware Filed Jan. 9, 1961, Ser. No. 81,625 2 Claims. (Cl. 257265) This invention relates to heat exchange apparatus of the rotary regenerative type and particularly to a unique arrangement for the removal of caked products of combustion and other deposits from the heat absorbent elements of such apparatus on which they become deposited and tend to accumulate during operation.

Rotary regenerative heat exchange apparatus of this type comprises essentially a housing having spaced end plates that are formed with openings through which hot gas and cooler air are directed. A rotor mounted for rotation about its axis in said housing includes a cylindrical rotor shell that is joined to a central rotor post by radial partitions to provide a series of sectorial compartments. Each such compartment is packed with a mass of heat absorbent material in order that upon rotation of the rotor the mass of heat absorbent material is alternately subjected to the hot gas and cooler air. Thus upon rotation of the rotor, heat from the hot gas is continuously transmitted to the cooler air through a heat absorbent intermediary.

During operation of the heat exchanger, soot and other products of combustion tend to collect on the heat absorbent elements and reduce the free area of the flow passageways therethrough so as to substantially reduce the effectiveness of the heat absorbent elements. Cleaning apparatus that supplies a quantity of air, steam or water to the deposits on the elements is customarily used to remove the deposits and open the flow passageways there through. However, certain deposits defy removal by such usual means and the principal object of this invention is therefore to provide an arrangement by which an abrasive material in the form of pellets or shot may be etfectively supplied during operation to the heat absorbent element of a rotary regenerative heat exchange apparatus whereby the deposited products of combustion may be removed therefrom.

A further object of this invention is to provide an arrangement by which the cleaning action is supplied only to a particular portion of the element that is subject to the greatest concentration of deposited combustion products.

The invention will be best understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional elevation of a rotary regenerative heat exchanger showing the basic arrangement of apparatus that comprises the invention.

FlGURE 2 is a horizontal section of the valving arrangement as seen from line 22 of FIGURE 1.

In FIGURE 1 the numeral designates the cylindrical shell of a rotor that is divided into sector shaped compartments by a series of radial partitions 12 that are connected to the rotor post 14 and to the rotor shell 10. The rotor post 14 is rotatably supported by bearings 15 and 16 and is rotated about its axis by driving means illustrated at 18. The rotor compartments each contain a mass of heat absorbent material, usually in the form of spaced metallic plates, which absorb heat from hot gases entering the preheater through a duct 20. After the hot gases pass over the metallic plates and transfer a portion of their heat thereto, the then cooled gases pass to an outlet duct 22 to which an induced draft fan (not illustrated) is usually connected. Upon rotation of the rotor about its axis a stream of cool air from inlet 23 passes over the heated plates to absorb heat therefrom before being directed to a boiler furnace or other place of use through an outlet duct 24. A housing 26 enclosing the rotor is provided at either end with end or sector plates 28 that are apertured at 32 and 34 to permit the streams of gas and air to be directed through the rotor.

The mass of heat transfer plates carried by the rotor 10 is in accordance with the invention divided into upper and lower element layers 36 and 38 respectively with an inter-element space 42 axially aligned with openings 44 that are evenly spaced, one to a sectorial compart ment, around the periphery of the rotor post 14. Hardened steel liners 46 are fitted to each opening 44 to provide maximum resistance to abrasion by a stream of cleaning pellets that are periodically directed through each opening 44 to the space 42 during operation of the cleaning device.

The apparatus for supplying the cleaning pellets to the inter-envelope space 42 comprises essentially a supply duct 48 that extends down through the hollow rotor post but is carried by the upper end plate 28 or other structure independent from the rotor in order that the supply duct may remain fixed while the rotor turns about. The lower end 54} of supply duct 48 lying within the rotor post is bent normal thereto and flared to present its outer periphery in substantial alignment with the liners 46 that surround the openings 44 in the rotor post. A cylindrical valve housing 52 surrounding the flared end portion of the supply duct is coaxial with the supply duct 48 and is secured thereto at 53 while an outlet duct 54 depending from the funnel shaped lower end of housing 52 is directed through the lower trunnion and support bearing 16 to a collecting line 58 that is also connected by means of a duct 60 with a collection hopper 62 subjacent outlet duct 22 for the hot gas.

The valve housing 52 has but a single radial opening 64 fixedly aligned with the flared end 50 of the supp y duct 48. The housing 52 slidably abuts the end edge of liners 46 to preclude fluid flow therebetween while the flared end 50 is spaced from the inner surface of housing 52 to permit pellets rebounding from liners 46 to fall back into the housing 52. A series of flow vanes 66 are axially spaced in the flared end 50 to project pellets therefrom to radially spaced portions of the rotor in order that each compartment may receive a concentration of pellets in accordance with the frontal area of the heat absorbent element carried thereby.

A pneumatic feeding device 68 collects pellets from ducts 58 and 60 and elevates them to a pellet release tank 69 where they are maintained under a residual pressure determined by a relief valve 70.

In operation pellets maintatined under pressure in pellet release tank 69 are directed down through duct 48 to its flared end 50 where the pellets are projected radially outward into the inter-element space 42. As the pellets fall and strike the element layer 38 on which excess products of combustion have accumulated, the deposited combustion products are freed from the element by the abrading action of the pellets. The combustion products are entrained in the gas stream while the heavier pellets descend to hopper 62 and to collecting line 58 where they are directed to release tank 69 by means of feeding device 68. As the rotor turns about its axis each opening 44 is sequentially aligned with the flared end 50 of duct 48 such that the heat absorbent element 38 of each compartment is periodically subjected to the abrading action of the pellets.

While this invention has been described with respect a.) to the embodiment illustrated in this drawing, it is evident that various changes may be made without departing from the spirit of the invention. It is therefore intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. Rotary regenerative heat exchange apparatus having a housing including spaced end plates formed with openings for the fiow therethrough of spaced streams of hot gas and cooler air; a rotor mounted in said housing having a cylindrical rotor shell; a rotor post coaxial with said rotor shell; radial partitions extending between the rotor post and rotor shell to provide a series of sectorial compartments therebetween; upper and lower layers of heat absorbent element having an inter-element space,

carried in each sectorial compartment; a series of circumferentially spaced ports in the rotor post in axial alignment with the space between element layers; an enclosed tank mounted independent from said rotor and adapted to carry a supply of cleaning pellets; duct means extending through the rotor post from said tank having a radially facing end port confronting the spaced ports of the rotor post; a cylindrical housing within the rotor post enclosing the radially facing end of said duct and having an opening therethrough in alignment with said end port in the end of said duct whereby pellets are directed through the housing opening to the inter-envelope space; and duct means depending from said cylindrical hous ing adapted to carry pellets that rebound into said housing after striking the inner end of the radial partitions.

2. Rotary regenerative heat exchange apparatus having a cylindrical housing including spaced end plates formed with openings for the flow therethrough of spaced streams of hot gas and cooler air; a rotor mounted for rotation within said housing having a cylindrical rotor shell; a rotor post coaxial with said rotor shell; radial partitions extending between the rotor shell and rotor post to provide a series of sectorial compartments therebetween; upper and lower element layers in each compartment spaced to include an inter-element space; a series of circumferentially spaced openings in the rotor post in axial alignment with the inter-element space; a pellet release tank above said rotor and mounted independent therefrom; duct means carried by the pellet release tank and extending through the rotor post; a flared pellet nozzle connected to said duct means extending normal thereto into confronting relation with the openings in said rotor post adapted to project a stream of pellets from said tank to the lower element layer; an inner housing within the rotor post enclosing the flared nozzle and including an opening in radial alignment therewith; a pneumatic feeding device; duct means directing pellets from said inner housing and said cylindrical housing to the pneumatic feeding device; and duct means interconnecting the pellet feeding device and the pellet release tank adapted to direct pellets under pressure to said tank whereby they may 'be continuously supplied to the compartments of the rotor.

References Cited in the file of this patent UNITED STATES PATENTS 2,762,610 Puhr-Westerheide Sept. 11, 1956 2,766,969 Cooper et al. Oct. 16, 1956 2,809,018 Broman Oct. 8, 1957 FOREIGN PATENTS 1,139,747 France Feb. 18, 1957 

